edomund

Anyone running 720CC X4 and a S-AFC with the O2 unplugged?

If so have any of you had a problem with your AFR being really rich when cruising under 70% throttle?

SureShot

At one time I had my low map dialed down as much as -20% at some of the lower RPM's.

edomund

Yeah I have my lo map dialed in perfectly for 60% throttle or more but when it's lower than that it goes super rich. It drops off like a ledge. You can watch it go from 14.7 AFR at say 70% then if you try to cruise at 69% holding it steady at 69% (not decelerating) it will be at 12 AFR. Even if you accelerate to 69% and hold it will stay at 12 AFR.

If I bring down the lo map to make the AFR right under 70% it will be very lean when cruising above that. Most of the time I am above 70% throttle even when cruising because the narrow band TPS on the S4 is so small but it bugs me I can't tune the lower TP at cruising correctly!

ed

SureShot

I think I may have seen that on mine.

The thing is, my O2 sensor is connected, so I'm almost always in closed loop at low throttle.

My guess is, that when it goes way below the low throttle set point, there is a bottom default zone that reverts to zero correction.
I have seen brief periods of rich AFR at very light throttle, but they go back lean before I can set the S-AFC to show its correction.

I may experiment with a lower low throttle set point with more low map (-) correction, and let it interpolate the wider span between the low & high maps.